Bug 50463

Bug Description:

This is a lost notify deadlock bug.
When log4j works with AsyncAppender, log appender threads put log events into a buffer and wait when the buffer is full, and a dispatcher thread dispatches events in the buffer. But when an exception happens inside the dispatch thread, the dispatcher thread just goes down and there will be no one to deal with the full filled buffer and notify the waiting appender threads. So the waiting appender threads keep waiting forever.
The following is an example of starvation thread dump:

Thread[main,5,main] is waiting:
   at java.lang.Object.wait(Native Method) 
   at java.lang.Thread.join(Thread.java:1186) 
   at java.lang.Thread.join(Thread.java:1239) 
   at org.apache.log4j.Test50463.logToFillBuffer(Test50463.java:78) 
   at org.apache.log4j.Test50463.main(Test50463.java:62) 

Thread[Thread-11,5,main] is waiting:
   at java.lang.Object.wait(Native Method) 
   at java.lang.Object.wait(Object.java:485) 
   at org.apache.log4j.AsyncAppender.append(AsyncAppender.java:104) 
   at org.apache.log4j.AppenderSkeleton.doAppend(AppenderSkeleton.java:230) 
   at org.apache.log4j.helpers.AppenderAttachableImpl.appendLoopOnAppenders(AppenderAttachableImpl.java:65) 
   at org.apache.log4j.Category.callAppenders(Category.java:203) 
   at org.apache.log4j.Category.forcedLog(Category.java:388) 
   at org.apache.log4j.Category.error(Category.java:302) 
   at org.apache.log4j.Test50463$FillBufferThread.run(Test50463.java:95) 

How To Reproduce:

This bug is reproduced under log4j 1.2.14 and JDK 1.6.0_33.
Execute the following scripts to run the test to reproduce the bug (assume the location of the log4j test project is log4j_test_home).

Linux:
${log4j_test_home}/scripts/50463.sh [--monitoroff]
Windows:
%log4j_test_home%\scripts\50463.bat [--monitoroff]

Example: Use monitor to report and terminate the program when forever waiting happens:
${log4j_test_home}/scripts/50463.sh

Turn off monitor:
${log4j_test_home}/scripts/50463.sh --monitoroff